Next Problem - Won't Prime...

[Touring5]

This is a continuation of my Poulan chain saw problem(s).

I replaced the broken/rotted tubing in the fuel tank. I actually had to replace two pieces as the fuel pickup goes like this: Filter> 1/8" tubing > barbed fitting > 3/16" tubing > primer bulb. Luckily I bought both sizes of tubing and was able to do that repair.

So now the next problem... I put it back together, filled the fuel tank half full and tried to prime it. No dice - the bulb doesn't fill. So I turned the saw on it's side and removed the fuel cap. When I press the primer bulb there are bubbles in the tank (i.e. bulb is forcing air into the pickup filter) and when I release the bulb I hear a sucking/whistling sound. After a little diagnostic operation I found that the bulb is acting like a check valve, in that when pressed the carb side is blocked and the air flows to the fuel tank - and when released the fuel tank side is blocked and the suction is on the carb side. This seems wrong to me. I even removed the primer bulb and confirmed that when pressed air flows out through the "Tank" fitting and when released air is sucked in through the "Carb" fitting. Is this correct, or am I missing something?

Bottom line is the bulb won't draw fuel because it blocks the fuel inlet when released - opening the suction to the carburetor. I am befuddled or stupid but either way a little assistance would be greatly appreciated.

[Before anyone asks, no I didn't reverse the hoses. Initially only one hose was removed from the primer - the fuel line. The primer has two different size fittings: 3/16" for fuel line (labeled "tank" or something to that effect) and a 1/8" fitting for the hose that runs to the carburetor (labeled "Inlet" or something to that effect).]

 

[yeehaw1960]

If you press the primer bulb and it's forcing air through the pickup tube (filter), it's definitely reversed.

 

[yeehaw1960]

Sorry. To be more specific, when you push the primer bulb in, it forces air into the tank through the line that enters the tank, but doesn't have a filter on it, thus forcing fuel through the filter and into the carb.

 

[Touring5]

Something has definitely gone awry with the primer assembly. In retrospect, it explains some of the problems with starting/running I had originally (before replacing the rotted tubing) - in that, with the tank full the coupling that the tubing rotted off of was still down in the fuel (so it would still be able to draw fuel). Anyway, I ordered a newer primer bulb assembly for a whopping $4.20 so that should get me either fixed or on to the next problem....

 

[Tom_T]

These purge systems have check valves in them. Where they are located depends on your carburetor setup. One or both are probably in the bulb assembly but not always so. You may have a bad valve, replacing the bulb assy may cure it. If I am reading your post correctly you are saying the gas is being sucked through the carb and dumped back into the tank when you operate the bulb? If so this is the correct fuel path.

 

[Touring5]

OK, mystery solved. I was mistaken about the primer bulb being faulty - instead it was me.

When I first investigated the problem I saw: A) the pickup/filter with a piece of rotted tubing attached (not connnected to anything), and B) a fitting with a small broken tube attached. So I reasoned that the filter/tubing connected to the fitting with rotted tubing. Actually the filter/tubing exits the tank through the top, which is not visible in the tank. The fitting I saw was, for lack of a better term, the purge return line.

Now I have to replace the tubing that feeds the carb. Of course this will require removing the carb because the tank opening is directly below it. My familiarity with the priming system was only from operation - now I see/understand how it works.


Thanks to both you guys for your responses.

 

[Touring5]

Replaced the "other" piece of tubing (inlet to carb), and the saw primes, starts, and runs like new!

 

[yeehaw1960]

See...you've used your hemostats twice....the world is your hemo!